Distillation of tar



June 23, 1936. W. M BYWATER msTIpLATIoN 0F TAR Filed July 8, 1931 7Sheets-Sheet 1 INVENR Vo-J' )4. raf/b1 vBY 162.. ATTORNEYS June 23,1936... y W, M. BYWATER 2,044,764

` DISTILLATION oF TAR Filed July 8, 1931 '7 Sheets-Sheet 2 ATTORNEYS.lumel 23, 1936. W. M. BYWATER @044,764

DISTILLATION OF TAR Filed VJuly e, 1931 'r sheets-sheet s INVENTQR 72@'xnwomaws June 23, 1936 w. M. BYWATER 1 2,044,764 A DISTILLATION OF TARI Filed July 8, 1951 l '7 Sheets-Sheet 4 'INVESTOR BY /-...Lwamir ATTORNEYS R E T. A W Y B M. W.

DI STILLATION OF TAR Filed July 8, 1951 '7 Sheets-Sheet 5 June 23, 1936w. M. BYWATER f DISTILLATION oF TAR 7 ySheets-Sheen 6 Filed July 8, 1951INVENTOR: B( ./Sr;

ATTORNEYS June 23A, 1936.. 'W M BYWATERv 2,044,764

DISTILLATION OF TAR Filed July a, 1931 7 sheets-sheet 7 @maar INVENTOR li.; @M 1mg-,M

ATTORNEYS Patented June 23, 1936 UNITED STATES PATENT OFFICE;

DISTILLATION F TAR Application July 8, 1931, Serial No. 549,429`

19 Claims.

This invention relates to the distillation of tar, etc., to producepitch and distillate oil kand the simultaneous recovery of tar acids ascarbolate, and includes both the method of distillation and apparatustherefor.

To recover tar acids from tar it is customary to distill the tar and toextract the resulting liquid distillate with an alkaline reagent. Thedistillate is preferably collected in fractions and one or more of thetar-acid-containing fractions is then extracted to recover tar acids.This method requires large tar-acid-oil storage facilities and extensiveliquid extraction tanks, etc.

According to the present invention, tar acids are recovered by alkalineextraction in the vapor phase, i. e., by bringing a solution of causticsoda or other alkaline reagent into intimate contact With vapors of taracids in admixture with vapors of non-acid oils. The tar acids areextracted by the caustic and recovered as carbolate Without necessarilycondensing any large proportion of non-acid constituents. In theapparatus employed, the tar-acid extraction is carried outsimultaneously with and as a part of the distillation.

In extracting tar acids in the vapor phase from admixture with vapors ofneutral oils, i. e. nonacid constituents, if the vapors are not too hotthe condensation of substantial amounts of neutral cils can be avoidedby using a hot, strong,

alkaline solution for the extraction, the heat effect of evaporation ofthe alkaline solution being insufficient to effect substantial coolingand condensation of vapors of non-acidicconstituents. In distilling tar,if the tar is heated to a sufciently high temperature to vaporize thegreater part of the tar acids, the vapors are at such a high temperaturethat it is impracticable to maintain a solution of caustic in contactwith them Without considerable evaporation. At temperatures of about 190to 210 C., however, hot commercial caustic solutions containing about 47to 50% of caustic can be employed toextract tar distillation vapors;although there will be some evaporation from such concentrated solutions`at this temperature, the amount will not cause undue anddisadvantageous-cooling of the vapors.

If the tar is heated to such a temperature that only the lower boilingconstituents are distilled, then the vapors may be treated `directlywith caustic, but if the vapors are at too high a temperature, theirtemperature must rstbe reduced by fractionally cooling them andcondensing the higher boiling constituents before bringing the residualvapors in contact with caustic.

I have found that by fractionally cooling the vapors from distilling tarso as to obtain taracid-containing distillate and then subjectingthedistillate while still hot to inert gas distillation, tar acids canreadily be recovered by vapor phase extraction of the gasesand vaporsresulting from this inert gas distillation and the tar acid recovery maybe carried on in conjunction with the tar distillation. My process isdesigned more particularly for the extraction of distillate obtained bythe condensation of vapors which leave the still at a temperature aboveabout 200 C. 15

According to this invention the vapors from the tar still are subjectedto fractional condensation inV any suitable Wayto obtain a high boilingtar-acid-Containing fraction and the tar acids are then vaporized fromthis fraction in 20 a eurent of inert gases, preferably by utilizationof the self-contained heat of the oil and without any further additionof heat. Y This inert gas distillation is -advantageously a. cyclicprocess, in which the inert gases pass in succession thru the oil, thenthrough a caustic extractor (when the tarracids are recovered `by directcontactwith an alkaline reagent), andare then recycled thru the oilfraction. All or Vonly a part of the gases may be recycled. The cycle`may include a condenser before or after thecaustic extractor or some`cooling may be eiiected within the caustic extractor. Any coolingwhich, may occur in the cycle is preferably regulated so. that,:at most,only a part of the oil vapors are condensed and the recycled gases, whenthey are again brought into contact with the distillate oil, containvaporsof neutral or non-acid constituents. These neutraloilV vaporspresent or inhibit the vaporizationof neutral oils from theoil fraction,but, owing to 40.

the removal of thetar acids `from the recycled gases by causticextraction in the vapor phase, tar'acids present Vin the distillate oilfraction are readily vaporized. 1n` this Way the tar acids areselectively distilled and the oil fraction after treatment Ycontains alower content of tar acids thanbeforetreatment; it may be asubstantially neutral oil, i. e., an oil substantiallyfree from taracids.

When the processis applied to a batch still operation, the tar isheated, and thevapors coming olf up to a temperature of about 200 C maybe treated in any of several'ways. They may-be treated, directly withstrong caustic for extractioniof the tar acids and subsequentlycondensed.

as neutral oil, or they may be condensed as acid oil and this acid oilmay be run to a tar-acid still for removal of the tar acids by inert gasdistillation. In any case, oil fractions coming off at vaportemperatures in excess of 200 C. are condensed and run 'to the tar-acidstill in which the tar acids are removed by inert gas distillation in amanner entirely similar to that previously described. This treatmentcontinues until such time as the tar-acid content of the vapors becomestoo low, or their commercial value becomes too small, to warrant furthertreatment.

When tar is continuously distilled in a simple still, then the vaporscoming off include the total oil vapors corresponding to the pitch beingmade. The vapors are fractionally condensed and a hot oil fractioncontaining tar acids is selected and sent to the tar-acid still forinert gas distillation, the operation of which is substantially the sameas that previously described. In a pipe still distillation the tar isheated and then flashed in a vapor box. The vapors are fractionallycooled to produce a tar-acid oil fraction which is treated for therecovery of tar acids. If low melting point pitch is produced,fractional condensation may not be necessary; the entire distillate maybe treated to recover its tar-acid content. In addition to theextraction of tar acids from the distillate, tar acids may also berecovered by treating any vapors leaving the fractional condenser thatremain uncondensed, at a temperature of 200 C., or lower, by treatingthese vapors directly with caustic solution.

When tar is continuously distilled in a series of simple stills, whichmay, for example, be arranged on the cascade principle, then vapors fromany of the first stills, which may be at a temperature lower than about200 C., may be treated directly by caustic for recovery of acids, butvapors coming from stills at higher temperatures than this are firstcondensed, either totally or fractionally, and the hot condensate,containing tar acids, is treated by inert gas for redistillation of thetar acids followed by subsequent recovery by extraction with caustic.

The apparatus of this invention includes a tar still and condensingmeans. Any suitable type of condenser may be employed. The condenser maybe a fractional condenser or total condenser. The condensation may occurin connection with a fractionating column. Ordinary reiiuxing means maybe used to advantage in separating distillate fractions. If tar acidsare to be recovered directly from the vapors from the still aftercondensation of one or more distillate fractions by contact with analkaline reagent, this extraction may take place in one section of afractionating column equipped for this purpose, or extraction may takeplace in any other suitable type of gas and liquid contact apparatus.

The receptacle in which the oil fraction is distilled by the inert gasesmay advantageously be a packed tower or a grid tower, although'anysuitable type of gas and liquid contact apparatus may be employed.

The caustic extraction tower may be a packed or grid tower. It isadvantageously constructed in such a way as to provide for two or morepassages of the gases and vapors thru it and with means for resprayingpartially saturated causticcarbolate solution into the gases. Freshcaustic is advantageously added to one of the towers and blended withcarbolate therein and sprayed into the gases before being drawn off intothe second tower in which it is again sprayed into the gases beforebeing drawn off as the make" of carbolate. It is advantageous to thusrecycle carbolate thru the extraction apparatus in admixture with thecaustic in order to provide for a large surface of liquid-gas contact. 5

When the tar is distilled by a continuous process the temperature atwhich the vapors leave the still will vary with the kind of tar treated,and the melting point of the pitch desired, etc. If the vapors leave thestill at a sufliciently high tem- 10 perature, one or more oil fractionswhich are not treated for tar acids may be condensed from the gasesbefore a tar-acid oil is obtained. In general, it will be desirable tocondense only part of the tar-acid-containing oils and then remove 15the tar acids from this condensate by distilling in a current of inertgases, and it will generally be preferable to cool the vapors to atemperature not lower than about 200 C. to obtain a fraction fortreatment according to this process.

Although the vapors may be cooled to an even lower temperature to obtaintar-acid distillate to be treated according to this invention, yet bycooling only to about 200 C., high boiling distillate will be recoveredat a temperature usually 25 somewhat above 200 C., and with sufiicientheat content to permit the distillation of tar acids in an atmosphere ofinert gas largely or entirely by its self-contained heat. Thenon-condensed vapors from the partial condenser can be extract- 30 eddirectly in the vapor phase at this temperature to recover tar acids. Ifthe oils are not suiiiciently hot to effect the distillation by theirselfcontained heat, they may be heated or the inert gases' may be heatedbefore they enter the appa- 35 ratus for the distillation of tar acids.

By proper regulation of the temperatures at which the vapors from thestill enter each section of the fractional condenser, and by properregulation of the removal of tar acids from one or more selecteddistillate fractions by inert gas distillation, tar acids of aparticular boiling range may be selectively recovered. For example,ordinary coke-oven tar may be heated and flashed and the resultingvapors may be cooled to a tem- 45 perature around 280 C. before theyenter the condenser in which that distillate fraction is condensed fromwhich tar acids are to be recovered.

In this condenser they may be cooled to about 200 C. Generally thecondensate obtained is at 50 a sufficiently high temperature(intermediate between the gas inlet and outlet temperatures), say 250C., to allow distillation of the tar acids by recirculation of an inertgas without the addition of heat. 55

By regulating the rate at which the gases are recirculated thru the oiland the temperature in the treating chamber, the amount of tar acidsvaporized is controlled.

The tar acids which remain in vapor form in 60 the uncondensed vaporsfrom the condenser may be extracted directly in the vapor phase bycontact with caustic solution, After the extraction of the tar acids invapor form, the resulting vapors may be cooled to condense one or more65 fractions of neutral oil.

Inert gasA is used herein to refer generally to a gaseous medium, whichis chemically inert to tar acids and caustic or other alkaline reagentemployed, and which is suitable for use as a "0 carrier for the tar-acidvapors. It is used to include condensable vapors such as steam and thevapors of neutral oils, as well as gases such as nitrogen, etc. Steam orother inert gas may be added to the inert gas system in carrying outthis 75 operation orthe inert gases. may be composed entirely ofuncondensed vapors resulting from the.

distillation. A vent to the system is provided to Atake care ofadditions or accumulations of steam orother inert gas or excess gasesand vapors that may be produced during the cycle, asby decomposition ofoil and vaporization of Va portion of the lower boiling oils beingtreated, and this vent is advantageously thru a condenser for condens.

ingand collecting any oil vapors contained in the vented gases.

In the inert gas distillation cycle in which the tar acids are distilledfrom the hot, higher boiling distillate, Vthe vapor phase extraction ofthe tar acids may be effected without any substantial cooling in thesystem so that the inert gases are recycled at a substantially constanttemperature.

However, if desired, oils may be condensed from the cycle either in thecaustic extractor thru vaporization of Water from the caustic solutionor. by the use of special cooling means in the caustic extractor, etc.,or oils may be condensed from the recycled gases and vapors before theyenter the caustic extractor, or after they have left the causticextractor. Oil condensed after the extraction of tar acids is neutraloil or oil of 10W tar-acid content, depending upon the degree ofcompleteness of the tar acid extraction in the caustic tower. Oilcondensed before the extraction of tar acids is a tar-acid-containingoil.

One oil fraction may be subjected to successive inert gas distillationsto remove differenttar acids. The hot condensate may first be treatedfor the removal of phenol which is the lowest boiling tar acid and aftera substantial recovery of phenol the oil may be drawn off into anothertreating chamber for the recovery of higher boiling tar acids by inertgas distillation. It may be necessary to heat the oil somewhat beforethe removal of the vhigher boiling tar acids or the gases employed maybe heated before entering the second treating chamber.

The invention will be further described in connection with theaccompanying drawings, but it isintended and is to be understood that itis not limited thereto.

In the drawings: Y

Fig. 1 shows the tar acid still and extractor in combination with a pipestill and fractionating column;

Fig. 2 is similar to Fig. 1 but shows a condenser following theextractor in the tar acid recovery cycle;

Fig. 3 shows a pipe still in combination with a series of fractionalcondensers equipped for carrying out this invention.

Fig. 4 is similar to Fig. 3 but shows a con; denser preceding theextractor in the tar acid recovery cycle;

Figs. 5 and 6 show diagrammatically a pipe still connected withfractional condensers, means for caustic extraction of the partiallycooled vapors and means for the recovery of tar acids from thecondensate from one of the condensers.

Fig. 7 shows a simple still equipped for carrying out the process ofthis invention as a batch process;

Fig. 8 shows a simple still equipped for carrying out the process ofthis invention as a continuous process; and

Fig. 9 shows a cascade of simple stills equipped for carrying out thisinvention.

In the various figures the same numeral is used to designate like partswith the addition of a distinguishing letter.

In .'distilling'tar in a pipe still it is heated in the coil 4or heatingtubes to a temperature above its initial boiling point and flashed inthe vapor box.,l The vapor box is ordinarily maintained at pressuresslightly above atmospheric although pressures higher or lower than thismay be employed, if desirable. Referring to Fig. 1, the tar is heated onpassing. thruthe pipe coil heater I and is then flashed into the vaporbox 2. The vapors pass to. the condensing system and theundistilledresidue, which is pitch, is drawn ofi thru the line 3 intothe receiver 4. This pitch maybe of high or low melting point, asdesired. The vapors pass from thevapor box thru the insulated 4main 5tothe fractionating column, which is composed of the sections 6, l, Band 9. Each of these sections comprises a set of cooling coils I0 in thetop with rectifying means below, which may be bubble-cap plates orsuitable grids or other packing.

The highest boiling oil fractions which condense in the sections 6 and1, will generally contain little or no tar acids of commercial value,although this will depend upon the kind of pitch being produced. Thesefractions are therefore generally not treated for tar acids. Thefraction condensed in section 8 contains valuable tar acids and is drawnoff into the treating chamber, or tar-acid still, II. The oil vaporssubsequently condensed in section 9 and in the worm condenser 9 willalso contain valuable tar acids. These may be recovered by extraction ofthe condensed oils or by extraction of the vapors before condensation,as described below. Furthermore, depending upon the conditions ofoperation, especially upon the melting point of the pitch produced, oilcontaining valuable acids may be produced in section 1 and this oil maythen be run into the tar-acid still II, together with oil from section 8and treated simultaneously with it, or it may be separately treated. Theneutral oil or oil of relatively 10W tar-acid content which results fromthis selective distillation of tar acids from the tar-acid-containingdistillate in the still II, is drawn off into the tank I8.

Fresh caustic is added to the caustic extractor I5 thru the feed pipeI9. Carbolate formed in the extractor together with fresh caustic isdrawn off thru the line 20, passed by the pump 2l to the heatinterchanger 22 and sprayed into the gases by means of the nozzles 23.Similarly, the partly saturated caustic-containing carbolate isWithdrawn thru the line 20', to the pump 2| and forced thru the heatinterchanger 22 to the sprays 23. The temperature of thecausticcarbolate solution is controlled by the heat interchangers 22 and22 so that there is little cr no condensation of neutral oils in thecaustic extractor. The carbolate formed is drawn oif thru the line 24and collected in the tank 25.

As one example of carrying out the process in the apparatus of Fig. 1,the treatment of cokeoven tar with a tar-acid content of 3% will beconsidered. The tar enters the heater I at a temperature in theneighborhood of C. It is heated in the pipe coil or tubular heater to atemperature of 400 C. and is ashed in the vapor box 2. The vapors leavethe Vapor box thru the mainI 5 at a temperature of about 380 C. andcontain oils boiling up to and above a temperature of 400 C. The pitchdrawn off from the Vapor box has a melting point in the neighborhood of210 F. and is suitable for use as fuel pitch. The fraction collectedfrom section 8 may boilfrom 198 C. to 270 C. and is drawn off into thetar-acid still II where it is treated for tar acids. This oilrepresents, for example, 15 to 20% of the total distillate and contains,for example, 20 to 40% of the tar acids present in the tar.

The treatment of the oil in the tar-acid still may be regulated torecover a desired percentage of its tar-acid content; for example, byrecirculating inert gases thru the still at a rate of 200 cubic feet pergallon of tar treated, and if the oil enters the still at a temperatureof 150-1'10 C., 'l5-90% of the tar acids in the oil will be recovered.'Ihe gases and vapors enter the caustic extractor at about -160" C., andare sprayed with caustic soda solution of about 49 Baume.

In carrying out the inert gas distillation, the uncondensed neutral oilsresulting from extraction of the tar acids may be recirculated and serveas a part of the inert gas, the balance being largely steam (which maybe continuously supplied thru thc pipe |3) or products of decompositionof the oil or air originally present in the system at the start. A bleedcondenser 26 is provided to vent any excess of gases to the atmosphereand maintain the inert gas distillation cycle under constant pressure,and to condense oil vapors from the vented gases.

Fig. 2 shows somewhat similar apparatus with a heater Ia and vapor box2a, a fractionating co1- umn and means for withdrawing condensate fromthe section 'Ia into the tar-acid still I la, but the cycle for theinert gas distillation includes in addition to the caustic extractor|50, a condenser 30. Both tar acid and neutral oils are distilled in thestill I Ia. In the caustic tower 5a tar-acid vapors are extracted andremoved from the cycle; The resulting gases include vapors of neutraloils. On cooling in the condenser 30 a portion of the neutral oils iscondensed. The condenser is not a total condenser but a partialcondenser so that the gases leaving the condenser 30 and returning tothe still la include vapors of neutral oils.

Adapting the example recited in connection with Fig. l to the apparatusshown in Fig. 2, with a tar-acid oil with a boiling range of 198 to 270and tar-acid content of about 10-12% drawn off from the section 'Ia intothe oil-treating tower Ila at a temperature of 15G-170 C., and withgases being recycled thru the treating chamber lia at the rate of 200cubic feet per gallon of tar distilled, neutral oil containing less than1.5% tar acids may be collected in the condenser 30. The oil drawn oninto the receiver |8a will necessarily be of different composition fromthe oil obtained by the process of Fig. l, because of removal of some ofthe oils in condenser 30 in addition to removal of tar acid.

Fig. 3 shows apparatus somewhat similar to the apparatus of Fig. l, butinstead of a fractionating column in conjunction with Condensers, singleoil Condensers are shown at lb, 8b, and 9b connecting with the Vapor box2b. Condensers of any suitable type may be employed, e. g. heatinterchangers in which the tar is preheated, or condensers using watero1' oil as the Vcooling medium. Instead of separate condensers 8b and9b, a single total condenser may be employed. Fig. 3 differs from Fig. 1in that the oil from the rst condenser 'Ib is drawn off into the stillIIb in which it is treated by inert gas distillation for recovery of taracids. The arrangement of Fig. 3 is used when a low melting point pitchis produced, since it will be generally found that the first oilcondensate contains tar acids of commercial value.

When using the arrangementvof Fig. 3, for example, tar may be heated inthe pipe coil heater Ib to a temperature of about 345 C., and flashed inthe vapor box 2b so that the vapors pass from the vapor box to thecondenser thru the main 5b at a temperature of about 330 C., and thepitch drawn ofl into the receiver 4b has a melting point of about F. Theoil fraction drawn 01T section 'Ib thru the line |21)` into the treatingtower IIb will have a boiling range of about 230 C. to over 350 C.

The apparatus of Fig. 4 shows a condenser 3| following the oil-treatingstill I Ic and before the caustic tower I 5c. Part of the oil vaporsleaving the tower I Ic are condensed and the gases cooled before beingbrought into contact with caustic. This arrangement is particularlyapplicable when the total first oil cut from the vapors leaving thevapor box 2c, which is withdrawn from section 1c, yields vapors duringthe inert gas distillation which are too hot to be brought into contactwith caustic solutions. It is also applicable when it is desired torecover part of the tar acids and the lower boiling oils condensed in'Ic with the heavy oil as a tar-acid oil condensate withdrawn from 3|into the receiver 3|.

Fig. 5 shows schematically apparatus for passing the vapors from thevapor box 2d, rst thru the condenser 8d from which a high boilingfraction containing little or no Valuable tar acids is recovered, thenthru the condenser 'Id from which 9 a fraction containing valuable taracids 1s recovered, then thru a caustic tower 32 and then thru acondenser 9d. The oil from the condenser 'Id is drawn oli into thetar-acid still d and after vaporizing the tar acids therefrom they areconverted to carbolate in the caustic tower |5d. Only a portion of thetotal Valuable tar acids in the tar is condensed in the condenser ld.Other tar acids pass thru the condenser Id in vapor form and these areextracted in the vapor phase in the caustic tower 32. Any suitable typeof gas-liquid-contact apparatus may be employed for bringing the causticinto contact with the tar-acid-containing gases. In Figs. 5 and 6 thecaustic towers are shown as packed towers.

The vapors enter condenser ld at such a high temperature that it is notpractical to extract tar acids from them in the vapor phase; therefore,they are cooled in this condenser to a temperature such that when theypass into the extractor 32 they can be extracted by direct contact withconcentrated caustic. This invention, however, offers a means ofreconverting into vapors the valuable tar acids which have beencondensed in the oil from section 'Id and recovering them as carbolatesimultaneously with the recovery of the tar acid vapors in extractor 32.From the caustic extractor 32 the gases pass to the condenser 9d, whichmay be a total condenser as shown, or several separate condensers. Inthis condenser neutral oils are recovered.

As an example of carrying out the process, cokeoven tar with a tar-acidcontent of 3% may be heated in the heater Id to a temperature of 400 C.,and flashed inthe vapor box 2d. The vapors leave the vapor box at atemperature of about 380 C., and are cooled in the condenser Ed to about300 C. In the condenser 'Id the gases are cooled to a temperature ofabout 200 C., or lower, and the oil condensate is drawn off into thetaracid still ||d in which it is treated for the recovery of tar acids.The vapors pass thru the caustic tower 32 without substantial coolingand are sprayed with a concentrated solution of caustic. This convertsthe tar acids tov carbolate, which is collected in the tank 33 and theextracted oil Y aolrtvcaA vapors passaonto the condenser 9d. Under theseconditions about.4045% of the tar acids lin the tar is condensed withthe oil withdrawn from the condenser ld and of this asA much as Sil-%may be recovered as oarbolate in the tower l5d. About 30-35% more of thetar acids in the tar may be recovered as carbolate in the extractor 32.The proportion of tar acids recovered in the condenser ld may be variedand the proportion ren covered Vas carbolate in the caustic tower 32will Vary accordingly, depending upon the conditions of operation.

In most respects the apparatus of Fig. 6 is the same as that shown inFig. 5 but the operation is changed in that the carbolate from thecaustic tower 32e is sprayed into the caustic tower |5e instead of beingseparately collected. Caustic is added to the tower 32e in excess overthat required for extracting the tar acids in the vapors leaving le, andthis excess is used for extracting tar acids from the gases and vaporsin the caustic tower I 5e. However, fresh caustic may be added to thetower 15e, if desirable.

In Figs. '7, 8 and 9 an ordinary tank still or simple still is shown.The still comprises a metal tank 5I which is heated from a hre-box 52.

Fig. 7 shows ap-paratus designed for recovering tar acids from a batchdistillation process. As the tar in the still is gradually heated,higher and higher boiling oils are given olf. Until the temperatureofthe vapors reaches 200 C. the vapors may be passed thru the causticYextractor 53 and there extracted directly with hot concentrated causticto produce carbolate. The vapors remaining after this extraction of taracids may then be passed to condensers to recover the remaining neutraloils. As the distillation progresses and the vapors leave the still at atemperature around 200 C. or higher, the vapors will no longer be passedthru the extractor 53 but will be passed to condensers. Two condensers54 and 55 are shown inthe drawings. The oil which condenses in thecondenser 54 is first extracted for tar acids and then as thetemperature of the vapors goes still higher it may be desirable to rstcool the vapors in the condenser 54 to condense high boiling oils whichare substantially free from valuable tar acids and then on furthercooling in the condenser 55 throw down a tar acid oil. Both of thecondensers 54 and 55 are connected with the tar-acid still Hf. Both ofthe condensers are also connected with oil storage tanks 54' and 55. Theoilfrom the condensers may be run to these storage tanks or the oil fromeither of these condensers may be run to another oil storage tank, or ifit is a tar-acidcontaining o-il it is run into the tar-acid still I lf.In the taracid still it is subjected to inert gas distillation while itis still hot 'and tar acids are extracted in the caustic extractor I5j.During the early stages of the distillation, when tar acids areextracted inthe extractor 53, neutral oils may be condensed in thecondensers 54 and 55 and be drawn 0E into suitable storage tanks. It isnot necessary that the tar acid be extracted from the vapors given offduring the early stages of the process, but :these vapors may be cooledto produce a tar-.acid oil.

As the recovery of tar acids does not take place simultaneously incaustic towers 53 and 51, one caustic tower can be employed to make bothextractions.v In this case by making suitable pipe connections vaporsfrom the still would run directly through caustic tower 53 until thevapor temperature reached 200 C.,- then the vapors would be made tobypass caustic tower 53 and oil condensed in condensers 54 and 55 wouldbe run intol inert gas still Ilf and the vapors from the inert gas stillpassed through caustic tower 53 for extraction.

In Fig. 8 the still is equipped for continuous distillation, the tarbeing fed continuously to the still and pitch being continuously drawnoff from it. The vapors pass thru the condensers El, 62 and 53 in seriesin which they are fractionally cooled. If a high melting point pitch isproduced heavy oil from the condenser 6| and possibly alsoI the oil fromthe condenser 52 will be drawn off into separate storage tanks and willnot be extracted for tar-acid content. The heavy oil may all becondensed in the condenser 0l and taracid oils may then be condensed inthe condensers 52 and E53. The tar-acid oils that are to be extractedmay be drawnV off in separate tar-acid stillsfor the separate recoveryof tar acids of different boiling range or they may be drawn off intothev same tar-acid still, Hg, as shown.

In Fig. 9 a plurality of tar stills 1|, 12, 13 and 14 are shown with thetar flowing thru them in series in cascade. The tar is subjected toprogressive distillation inthe variousstills and pitch of the desiredmelting point is drawn off from the last still of the series. Light oilsare distilled offI in the still 'll and condensed in the condenser 15.These light oils are drawn 01T to a suitable storage tank. If highmelting point pitch is produced the heaviest oils vaporized in the still'i4 and condensedin the condenser 'i6 are likewise advantageously drawnoff into separate storage tank. One or both of the intermediatefractions distilled in the stills 'l2 and 'i3 and condensed in thecondensers 71 and'l are drawn off into the tar-acid still l lh andtreated for the recovery of tar acids.

Different types of condensing means may be employed in connection withthe different stills shown. Tar acid extractors of various types may beemployed. In the tar-acid cycle in which the tar acids are vaporized ininert gases and then extracted in a caustic extractor, condensers may beemployed either before or after the caustic extractor, as indicated inFigs. 4 and 2, respectively, and the apparatusshown in any one of thefigures may be modified or added to in this or other ways all within thescope of this invention.

Although the invention is described more particularly as applied to thedistillation of coke-oven tar, it may be applied to the treatment ofother tar-acid-containing tars such as vertical retort tar, gas-retorttar and other coal tars, and also to the treatment of distillate such ascoal-tar distillate.

I claim: l

1. The method of treating Vliquid tar-acidand neutral-oil containinghydrocarbon material, which comprises distilling tar acids and'neutraloils therefrom, cooling the vapors resulting from the distillation tocondense both tar acids and neutral oils, and then distilling tar acidsfrom this condensate by the self-contained heat thereof.

2. The method of treating a batch of tar-acidand neutral-oil-containinghydrocarbon material, which comprises distilling the same, coolingvapors which distill oir at a temperature above 200 C. so as to condensetar acids and neutral oils therefrom, and then distilling tar acids fromthe condensate in a current of inert gases while the condensate is stillat an elevated temperature.

3. The method of treating tar-acidand neutral-oil-containing hydrocarbonmaterial, which comprises distilling the same by a process of continuousdistillation according to which the vapors leave the still at atemperature of at least 200 C., cooling the vapors to condense tar acidsand neutral oils therefrom and vaporizing tar acids from the condensatein a current of inert gases while the condensate is still at an elevatedtemperature.

4. The method of treating liquid tar-acidand neutral-oil-containinghydrocarbon material, which comprises distilling tar acids and neutraloils therefrom by a process according to which the vapors leave thestill at a temperature of at least 200 C., cooling the vapors resultingfrom the distillation to condense both tar acids and neutral oils andthen distilling tar acids from the resulting condensate in a current ofinert gases by the self-contained heat of the condensate.

5. The method of distilling tar, which comprises distilling tar acidsand neutral oils therefrom at a temperature of at least 200 C., coolingthe resulting oil vapors to produce a tar-acid-containing distillate,distilling tar acids from the distillate, using the self-contained heatof the distillate in effecting the distillation, and extracting taracids from the resulting vapors by direct contact with a causticalkaline reagent.

6. The method of treating liquid tar-acidand neutral-oil-containinghydrocarbon material, which comprises heating the material to atemperature such that, on flashing, distillate comprising tar acids willdistill therefrom, flashing the heated material, condensing from theresulting vapors an oil fraction comprising tar acids, and distillingtar acids from this fraction in a current of inert gases while thefraction is still at an elevated temperature.

7. 'I'he method of treating liquid tar-acidand neutral-oil-containinghydrocarbon material, which comprises distilling tar acids therefrom ata temperature above 200 C., condensing from the resulting vapors an oilfraction comprising tar acids, distilling tar acids from this fractionin a current of inert gases including neutral oil vapors, spraying acaustic alkaline solution into the vapors resulting from the inert gasdistillation soas to extract tar acids, and recycling at least a portionof the gases and resulting neutral oil vapors into contact with the oilfraction.

8. The method of distilling coal tar, which comprises distilling taracids and neutral oils from the tar, cooling the resulting vapors tocondense neutral oils and part of the tar acids therefrom leavinguncondensed tar acid vapors, vaporizing tar acids from this condensateand extracting tar acids from the vapors by direct contact with analkaline reagent, and extracting tar acids from the uncondensed vaporsby bringing them into direct contact with a caustic alkaline reagent,thereby removing tar acids from uncondensed vapors in the form of theiralkaline salts.

9. The method of treating coal tar, which comprises heating the tar tosuch a temperature that, on ashing, tar acids will vaporize, flashingthe heated tar, cooling the resulting vapors so as to obtain a tar acidoil, vaporizing tar acids from the resulting condensate by theself-contained heat of the condensate, and extracting tar acids from thevapors by bringing a caustic alkaline reagent into direct contacttherewith.

10. The method of treating tar, which comprises distilling tar acidsfrom the tar, cooling the resulting vapors to condense only a part ofthe tar acids, extracting the resulting vapors with an excess of causticalkali solution thereby forming a caustic-carbolate solution, drawingthe tar acid oil from the condenser off into a tar acid still,vaporizing tar acids from the tar acid oil in the tar acid still whilethe tar acid oil is still hot, and bringing the caustic carbolatesolution from the caustic extractor into contact with the resultingvapors to extract tar acids therefrom.

11. Apparatus for the distillation of tar cornprising a pipe coil, aVapor box, means for heating the pipe coil, means for passing tai`through the pipe coil to the vapor box, a condenser, means for passingvapors from the vapor box thru the condenser, a tar-acid still, avcaustic extractor adapted to contact caustic alkali with the tar acidvapors and means for passing vapors and gases from the tar-acid still tothe caustic extractor, and means for drawing oil off from the condenserto the tar-acid still.

12. Apparatus for the distillation of tar comprising a pipe coil, avapor box, means for heating the pipe coil, means for passing tarthrough the pipe coil to the vapor box, a condenser, means for passingvapors from the vapor box to the condenser, a tar-acid still, a causticextractor adapted to contact caustic alkali with the tar acid vapors,means for repeatedly recirculating vapors serially thru the tar-acidstill and the caustic extractor, and means for passing condensate fromthe condenser to the taracid still.

13. Apparatus for the distillation of tar cornprising a tar still, atleast two condensers, means for passing vapors from the still thru afirst condenser and then thru the other condensers in series, a taracid, means for conveying condensate from at least one of thecondensers, not the rst condenser, to the tar acid still, a causticextractor adapted to contact caustic alkali with the tar acid vapors,means for repeatedly recycling vapors serially thru the tar acid stilland the caustic extractor.

14. Apparatus for the distillation of tar comprising a tar still, acondenser, means for passing vapors from the still to the condenser, atar acid still, means for passing condensate from the condenser to thetar acid still, a caustic extractor adapted to contact caustic alkaliwith the tar acid vapors, a second condenser, means for repeatedlyrecycling gases thru the tar acid still thru the caustic extractor andthen thru the second condenser in series.

15. Apparatus for the distillation of tar comprising a tar still, acondenser, means for passing vapors from the still to the condenser, atar acid still, means for passing condensate from the condenser to thetar acid still, a secondu condenser, a caustic extractor adapted tocontact caustic alkali with the tar acid vapors and means for repeatedlyrecycling gases thru the tar acid still, the second condenser and thecaustic extractor in series.

16. Apparatus for the distillation of tar comprising a tar still, acondenser, a caustic extractor adapted to contact caustic alkali withthe tar acid vapors, means for passing vapors from the still thru thecondenser and then thru the caustic extractor, a tar-acid still, meansfor drawing condensate off from the condenser to the tar-acid still, asecond caustic extractor, and means for passing vapors from the tar-acidstill to the second caustic extractor.

1'7. Apparatus for the distillation of tar comprising a tar still, acondenser, a caustic extractor adapted to contact caustic alkali withthe tar acid vapors, means for passing vapors Afrom the still thru thecondenser and then thru the caustic extractor, a tar-acid still, meansfor drawing condensate 01T from the condenser to the tar-acid still, asecond caustic extractor, means for passing vapors from the tar-acidstill to the second caustic extractor and means for conveying carbolatefrom th e first caustic eX- tractor to the second caustic extractor.

18. Apparatus for the distillation of tar comprsing a tar still, threecondensers, means for passing vapors from the still thru the condensersin series, an inert gas still, a caustic extractor adapted to Contactcaustic alkali with the tar acid vapors, means for recycling gases thruthe inert gas still and the caustic extractor, means forconveyingcondensate Without substantial reduction in temperature from the secondcondenser of the series to the inert gas still and means for separatelycollecting condensate from the rst and third condensers.

19. The method of recovering tar acids fro-rn tar, which comprisesdistilling the tar, cooling the resulting vapors to condense part butnot all of the tar acid vapors thereby producing taracid-containingcondensate, vaporizing tar acids from the condensate While still hot ina current of inert gases containing neutral oil vapors, cooling theresulting gases and vapors to condense a part of the tar acid oil vaporsand then extracting remaining gases and vapors for tar acids by contactwith an alkaline reagent.

WILFRED M. BYWATER.

